Objective: Intestinal microbiota are prominent in the etiology of irritable bowel syndrome (IBS). In this exploratory study, we investigated short- and long-term changes in the microbiota of IBS patients after intervening with a low-FODMAP diet (LFD) or 8-strains probiotics (Bifidobacterium, Lactobacillus and Streptococcus) using a standardized microbiota characterization test intended for routine use.

Materials and Methods: We analyzed data and fecal samples collected in a previous trial from non-comorbid IBS patients before treatment, and then again after four weeks and one year of treatment. Response to treatment was defined by a reduction in the IBS-SSS score, and the gut microbiota were characterized using the standardized and CE-marked GA-map® Dysbiosis Test Lx.

Results: Of the 25 responders to either treatment, two of the 22 with fecal samples available were dysbiotic at baseline, increasing to eight out of 19 after four weeks; after one year all responders providing a sample were normobiotic (n=15). After four weeks, the abundance of Bacilli, Lactobacillus spp. and Streptococcus salivarius ssp. thermophilus were temporarily increased in the 8-strains probiotics responder group (p<.05), while for LFD responders Anaerobutyricum hallii had decreased. There was a greater abundance of Ruminococcus gnavus at baseline in those responding to probiotics than in those responding to LFD.

Conclusions: In addition to improving IBS symptoms, sustained LFD or repeat 8-strains probiotics tended to temporarily alter the microbiota profile in responders. Microbiota characterization is a promising tool for monitoring IBS treatments; however, more extensive studies in treatment and monitoring are needed.